/*
 * Copyright 2000-2014 JetBrains s.r.o.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package com.intellij.util.containers;

import java.util.Iterator;
import java.util.NoSuchElementException;

public abstract class SingletonIteratorBase<T> implements Iterator<T> {
    private boolean myVisited;

    @Override
    public final boolean hasNext() {
        return !myVisited;
    }

    @Override
    public final T next() {
        if (myVisited) {
            throw new NoSuchElementException();
        }
        myVisited = true;
        checkCoModification();
        return getElement();
    }

    protected abstract void checkCoModification();

    protected abstract T getElement();
}